[vk] this is a hacky hacky workaround.

There seems to be some werid crash if nvidia libGL is being pulled by
cairo in some certain order.

http://code.google.com/p/fcitx/issues/detail?id=671

we notice it have something to do with pthread (cloudpinyin), and maybe
glib (spell), I have no idea about how nvidia's evil libGL do such bad
thing, but let's have a try..